{"data":{"fields":"term_definition","term_definition":"
Probably the oldest form of crossed axis gearing.\nUsually the axes are at right angles. The worm is a\ngear with one or more teeth in the form of screw\nthreads. The gear member is a disc with teeth on\nthe periphery which fit the shape of the worm.\nThis type of gearing is particularly suited to high\nratios. With single thread worms, ratios from 30\/1\nto 300\/1 or even higher are practical. When lower\nratios are required, a mulitple thread worm is used,\nwhich is harder to make with accuracy.\nWorm gear drives are considered the smoothest and\nquietest form of gearing when properly applied and\nmaintained. They should be considered for the following\nrequirements: High ratio speed reduction,\nlimited space, right angle (non-intersecting) shafts,\ngood resistance to back driving. General nomenclature\nhaving been applied to spur and helical gear\ntypes, may also be applied to worm gearing with\nthe addition of worm lead and lead angle, number\nof threads (starts) and worm gear throat diameter.\nThe efficiency of a worm gear drive depends on the\nlead angle of the worm. The angle decreases with\nincreasing ratio and worm pitch diameter. For\nmaximum efficiency the ratio should be kept low.\nDue to the sliding action which occurs at the mesh\nof the worm and gear, the efficiency is dependent\non the lead angle and the coefficient of the contacting\nsurface.<\/div>
\"ED182a\"<\/div>
\"ED-181a\"<\/div>
\"ED182a\"<\/div>
\"ED-181a\"<\/div>"}}